compiler: Introduce operator specialization

[EdCaunt]

WIP - the intention is to allow users to build an operator as per usual, then generate single-use "specialised" versions of it with hardcoded values in the generated code to free up registers

[codecov]

Codecov Report

❌ Patch coverage is 97.08738% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.09%. Comparing base (a00cca8) to head (0b445af).
⚠️ Report is 20 commits behind head on main.

Files with missing lines	Patch %	Lines
devito/operator/operator.py	88.00%	2 Missing and 1 partial ⚠️
tests/test_specialization.py	98.50%	1 Missing and 1 partial ⚠️
devito/ir/support/guards.py	85.71%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2812      +/-   ##
==========================================
+ Coverage   83.01%   83.09%   +0.07%     
==========================================
  Files         248      249       +1     
  Lines       50957    51260     +303     
  Branches     4489     4505      +16     
==========================================
+ Hits        42303    42592     +289     
- Misses       7883     7900      +17     
+ Partials      771      768       -3     

Flag	Coverage Δ
pytest-gpu-aomp-amdgpuX	68.37% <53.62%> (-0.13%)	⬇️
pytest-gpu-nvc-nvidiaX	68.93% <53.62%> (-0.10%)	⬇️

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